Analysis of guided and leaky modes of circular waveguides and realization of mechanical tunable metamaterial and devices

The guided and leaky mode characteristics for planar dielectric structures are relatively well known, due to its various kind of applications. However, the investigation to the modes characteristics for a circular rod structure is relatively rare, especially for the leaky modes, despite the rod structure is very simple and useful. Accordingly, in the first part of the thesis, we analyze the guided and leaky modes for a circular dielectric rod in detail. The analysis is carried out in several steps. First, by considering the field distributions outside the rod, the modes are well defined and classified based on their physical meanings. The relations for the mode solutions using different types of special functions and Riemann sheets are figured out. Further, completed forms of characteristic equations used to solve different modes are presented explicitly. Second, in order to solve this nonlinear characteristic equation efficiently and accurately, we employ iterative methods and spent lots of efforts in deriving the initial guess expression in a simply but efficient form. Through using the asymptotic expansion method and employing the Lambert W function, we derive the initial guesses around the cutoff frequency, low frequency limit and high frequency limit for both TM and TE cases. Finally, the numerical results are presented for the complex transverse propagation constants of proper and two types of improper modes for both cases. Some of the improper modes have not been shown in literatures. Next, we extend the analysis to the circular rod with negative permittivity and permeability (double negative material (DNG)). Following the same analysis procedure for the conventional dielectric circular rod, first, we derive the characteristic equation for the DNG case and de fine different types of modes. Second, we expand the characteristic equation asymptotically and then find the initial guess expression for different types of modes around the cutoff, high frequency limit and low frequency limit. Finally, using these initial guesses we solve the char acteristic equation with iterative methods and find the dispersion curves. xi The electromagnetic (EM) material property of simultaneous negative permittivity and per meability we use for the DNG rod analysis actually can not be found in nature so far. The method in generating material with DNG property is using metamaterials. In the second part of the thesis we introduce metamaterials, and discuss our work of realizing tunable metamate rials in detail. This type of tunable property allows the metamaterial device to overcome the drawback of fixed and limited bandwidth from the conventional metamaterials. We start it from presenting a novel tunable and flexible SRR-based meta-atom capable of tuning its EM response characteristics over a broad frequency range by simple mechanical stretching. First, we design and simulate a meta-atom with a liquid metal as the resonator material. The liquid metal is patterned to be a SRR structure and embedded inside a highly stretchable silicone elastomer. Due to its liquid nature, the liquid metal-based SRR could flow in response to an applied strain, and compliant to change from the encasing elastomer as the meta-atom being stretched and twisted. Therefore, through simple mechanical stretching, the shape of the SRR is changed. Correspondingly, the equivalent capacitance and inductance of the SRR are adjusted, thus tuning the resonance frequency of the meta-atom. The shifting trend of the resonance frequency with different stretching orientations is predicted by a simple circuit mode, and verified from the experiment. Next, we extend the idea of meta-atom to the meta-skin, which is composed of an array of meta-atoms. This meta-skin performed as a tunable selective surface with a wide resonance frequency tuning range when being stretched. Further, due to its flexibility, this meta-skin can function as a flexible “cloaking” surface in suppressing the scattering from the dielectric ob ject. As examples, we demonstrate frequency selective responses of multilayer meta-skins with different stretching ratio in the planar direction. Also, we investigate scattering suppression effect of the meta-skin coated on a finite-length dielectric rod in free space. Benefit from the liquid metal and highly stretchable elastomer, we design and realize a directivity reconfigurable two-arm spiral antenna. This new device has the ability to reconfig urate the radiation pattern along the main lobe direction by control the shape of the antenna, as the radiation pattern becomes sharper, directivity is optimized. Finally, the directivity, efficiency, and axial ratio with different dome height, operating frequencies are presented

Importance of 3D and Inkjet Printing For Tony Stark and the Iron Man Suit

For decades we have used printers to print superheroes on the pages of comic books but could printing technologies actually be used to print real life superheroes? 3D and functional printing technologies have advanced greatly in recent years and even though these technologies cannot be used to print heroes themselves, they can certainly be used for equipment manufacturing. One character that could or may use 3D printing to rapidly produce prototypes and final versions of new technologies is Tony Stark. As the inventor and primary user of the Iron Man suit, Stark has designed a wearable suit that is not only a weapon but also protects him. However, in battle the suit can become damaged and require urgent repairs. To aid in these repairs, Tony Stark could turn to 3D printing technologies to produce new components for the suit. In this paper we will outline 3D printing technologies and describe their current applications. We will then discuss how 3D printing is being used to print electronics and the ramifications for Tony Stark, his Iron Man suit and the potential use for a real Iron Man suit

Scalable Microfabrication Procedures for Adhesive-Integrated Flexible and Stretchable Electronic Sensors.

New classes of ultrathin flexible and stretchable devices have changed the way modern electronics are designed to interact with their target systems. Though more and more novel technologies surface and steer the way we think about future electronics, there exists an unmet need in regards to optimizing the fabrication procedures for these devices so that large-scale industrial translation is realistic. This article presents an unconventional approach for facile microfabrication and processing of adhesive-peeled (AP) flexible sensors. By assembling AP sensors on a weakly-adhering substrate in an inverted fashion, we demonstrate a procedure with 50% reduced end-to-end processing time that achieves greater levels of fabrication yield. The methodology is used to demonstrate the fabrication of electrical and mechanical flexible and stretchable AP sensors that are peeled-off their carrier substrates by consumer adhesives. In using this approach, we outline the manner by which adhesion is maintained and buckling is reduced for gold film processing on polydimethylsiloxane substrates. In addition, we demonstrate the compatibility of our methodology with large-scale post-processing using a roll-to-roll approach

Self-Powered Wearable Biosensors

Wearable biosensors hold the potential of revolutionizing personalized healthcare and telemedicine. Advances in chemical sensing, flexible materials, and scalable manufacturing techniques now allow wearables to detect key physiological indicators such as temperature, vital signs, body motion, and molecular biomarkers. With these systems operating on the skin, they enable continuous and noninvasive disease diagnosis and health monitoring. Such complex devices, however, require suitable power sources in order to realize their full capacity. Emerging wearable energy harvesters are attractive for addressing the challenges of a wearable power supply. These harvesters convert various types of ambient energy sources (e.g., biomechanical energy, biochemical energy, and solar energy) into electricity. In some circumstances, the harvested electrical signals can directly be used for active sensing of physiological parameters. On the other hand, single or hybrid wearable energy harvesters, when integrated with power management circuits and energy storage devices, could power additional biosensors as well as signal processing and data transmission electronics. Self-powered sensor systems operate continuously and sustainably without an external power supply are promising candidates in the next generation of wearable electronics and the Internet of Things. This Account highlights recent progress in self-powered wearable sensors toward personalized healthcare, covering biosensors, energy harvesters, energy storage, and power supply strategies. The Account begins with an introduction of our wearable biosensors toward an epidermal detection of physiological information. Advances in structural and material innovations enable wearable systems to measure both biophysical and biochemical indicators conformably, accurately, and continuously. We then discuss emerging technologies in wearable energy harvesting, classified according to their capability to scavenge energy from various sources. These include examples of using energy harvesters themselves as active biosensors. Through seamless integration and efficient power management, self-powered wireless wearable sensor systems allow real-time data acquisition, processing, and transmission for health monitoring. The final section of the Account covers the existing challenges and new opportunities for self-powered wearable sensors in health monitoring and human–machine interfaces toward personalized and precision medicine

Flexible and stretchable power sources for wearable electronics.

Flexible and stretchable power sources represent a key technology for the realization of wearable electronics. Developing flexible and stretchable batteries with mechanical endurance that is on par with commercial standards and offer compliance while retaining safety remains a significant challenge. We present a unique approach that demonstrates mechanically robust, intrinsically safe silver-zinc batteries. This approach uses current collectors with enhanced mechanical design, such as helical springs and serpentines, as a structural support and backbone for all battery components. We show wire-shaped batteries based on helical band springs that are resilient to fatigue and retain electrochemical performance over 17,000 flexure cycles at a 0.5-cm bending radius. Serpentine-shaped batteries can be stretched with tunable degree and directionality while maintaining their specific capacity. Finally, the batteries are integrated, as a wearable device, with a photovoltaic module that enables recharging of the batteries

Open-ended capstone project: designing and manufacturing of a low-cost carbon fiber reinforced composite suborbital rocket payload housing using a 3D printed core

Composite materials are utilized in many industries today due to its high performance and lightweight. However, the part manufacturing process of traditional composites is complicated and often involves high cost. The molds used for composite manufacturing are usually one of the contributors to the high part manufacturing cost. The authors demonstrated in this paper a manufacturing process for a carbon fiber reinforced composite rocket payload housing using an additively manufactured polylactic acid (PLA) payload housing core. The paper also demonstrates the designing and manufacturing of a functional product, which was used in a real-life application, achieved by college undergraduate students. The payload housing was designed to maximize space efficiency and the performance of the designed payload housing was simulated to verify that it met the structural requirements. Carbon fiber reinforced composites were wrapped and cured on the printed core using a wet layup technique. This process did not require traditional composite manufacturing molds, which resulted in significantly lower part manufacturing cost compared to a traditional composite part manufacturing processes using a mold. The carbon fiber-reinforced composite rocket payload housing was successfully built and mounted to a suborbital autonomous rocket and launched

A micro-incubator for cell and tissue imaging

International audienceA low-cost micro-incubator for the imaging of dynamic processes in living cells and tissues has been developed. This micro-incubator provides a tunable environment which can be altered to study the response of cell monolayers for several days as well as relatively thick tissue samples and tissue engineered epithelial tissues in experiments lasting several hours. Samples within the incubator are contained in a sterile cavity closed by a gas permeable membrane. The incubator can be positioned in any direction and used on an inverted as well as on an upright microscope. The temperature is regulated with a Peltier system controlled with a sensor positioned close to the sample to be able to compensate for any changes in temperature. Rapid changes in the environment can be applied to the sample because of the fast response of the Peltier system and the sample's adaptations to induced changes in the environment can be monitored. To evaluate the performance of the micro-incubator we report on studies using cultured cells in monolayers, on monolayers of cells stretched to breaking point on a distensible membrane, on cells in open 3D fibrous scaffolds and on fluorescently labelled polymersome penetration into 3D tissue engineered oral mucosa

HRS: Rover Technologies

No abstract availabl

Design of Electrode Materials for Stretchable Triboelectric Nanogenerators

Triboelectric nanogenerator (TENG), a recently emerging technology that is based on the combination of triboelectric effect and electrostatic induction, has been found to be a promising strategy to harvest large amount of underutilized and low-frequency mechanical energy. One major challenge for TENGs is that the practical application requires flexible, deformable, multifunctional materials to ensure its favorable accommodation to arbitrary surfaces or moving object or harsh environment. Recent research interests mainly focus on the design and fabrication of electrode materials for TENG, making it a perfect candidate for wearable power source. In this chapter, we will introduce a couple of recent achievements regarding highly flexible/deformable TENGs based on stretchable electrodes, including geometrically designed electrode, mixture of conductive materials with elastomeric materials and intrinsically stretchable electrode, etc. In addition, we will address stretchable and self-healing electrodes of flexible TENGs for potential wearable and implantable electronics